Blank masks for extreme ultra violet lithography, methods of fabricating the same, and methods of correcting registration errors thereof

ABSTRACT

Blank masks for extreme ultraviolet (EUV) photolithography are provided. The blank mask includes a substrate having a first surface and a second surface which are opposite to each other, a reflection layer disposed on the first surface of the substrate to reflect extreme ultraviolet (EUV) rays, an absorption layer disposed on the reflection layer opposite to the substrate to absorb extreme ultraviolet (EUV) rays, and a conductive layer disposed on the second surface of the substrate to expose portions of the substrate. Related methods are also provided.

CROSS-REFERENCES TO RELATED APPLICATIONS

The present application claims priority under 35 U.S.C 119(a) to KoreanApplication No. 10-2012-0083536, filed on Jul. 30, 2012, in the Koreanintellectual property Office, which is incorporated herein by referencein its entirety as set forth in full.

BACKGROUND

Embodiments of the present disclosure generally relate to photo masksused in fabrication of semiconductor devices and, more particularly, toblank masks for extreme ultraviolet (EUV) lithography, methods offabricating the same, and methods of correcting registration errorsthereof.

Semiconductor devices are manufactured using various unit processes suchas a deposition process, a lithography process, an etching process, adiffusion process, an impurity implantation process and/or the like. Thelithography process may be performed with a photo mask including circuitpatterns, and the shapes of the circuit patterns may be transferred ontoa wafer during the lithography process. As the semiconductor devicesbecome more highly integrated, sizes of the circuit patterns of thephoto mask have been continuously reduced. Thus, there may be somelimitations in fabricating the photo masks. In particular, as thesemiconductor devices are scaled down to have a minimum feature size ofabout 30 nanometers or less, there may be still limitations intransferring the fine patterns having line widths of about 30 nanometersor less on a wafer with a lithography apparatus that employs argonfluoride (ArF) lasers generating deep ultraviolet (DUV) rays as lightsources. Thus, extreme ultraviolet (EUV) lithography processes have beenproposed to overcome the limitations of the lithography processutilizing the deep ultraviolet (DUV) rays.

The EUV lithography processes may use EUV rays having a wave lengthwithin the range of about 13.2 nanometers to about 13.8 nanometers,which is shorter than wavelengths of lights generated by KrF lasers orArF lasers. The EUV rays may be more readily absorbed into most ofmaterial layers and may have a refractive index of about one in most ofmaterial layers. Thus, it may be difficult to apply refracting opticalsystems used in the conventional lithography processes with visible raysor general ultraviolet rays to the EUV lithography processes. For thereasons described above, the EUV lithography processes employ reflectingoptical systems (also referred to as mirror optical systems), forexample, reflection type photo masks and mirrors.

The reflection type photo masks used in the EUV lithography processesmay be configured to include a mask substrate and a light reflectionlayer on the mask substrate. The light reflection layer may include aplurality of molybdenum (Mo) layers and a plurality of silicon (Si)layers which are alternately stacked. That is, the light reflectionlayer may be a laminated layer. Meanwhile, circuit patterns of thereflection type photo masks may be formed of a light absorption layer,and shapes of the circuit patterns may be transferred onto a wafer. Thelight absorption layer and the light reflection layer may be formedusing an ion beam sputtering technique or a magnetron sputteringtechnique.

When the light absorption layer and the light reflection layer areformed on the mask substrate, the mask substrate is supported by asupporting member, for example, a mechanical chuck or an electrostaticchuck. The mechanical chuck may cause vibration of the mask substrateduring the process for forming the light absorption layer or the lightreflection layer. Thus, the electrostatic chuck rather than themechanical chuck may be widely used as the supporting member. Theelectrostatic chuck may be used to support the photo mask even when thecircuit patterns of the photo mask are formed or the photo mask ishandled during the lithography process. Thus, a conductive layer may beformed on a surface of the reflection type photo mask opposite to thecircuit patterns and alignment marks to fix the reflection type photomask on the electrostatic chuck employed in an EUV lithographyapparatus. In general, the conductive layer on the reflection type photomask may include an opaque material blocking lights, for example, achrome nitride layer, and an entire back side surface of the masksubstrate may be cover with the conductive layer.

Recently, high overlay accuracy of the photo masks has been increasinglydemanded with reduction of design rules of the semiconductor devices,and improvement of mask registration errors has been continuouslyrequired. In the event that an ArF light source is used in a lithographyprocess, the mask registration errors may be corrected by irradiating alaser onto a back side surface of a photo mask to deform a masksubstrate (e.g., a quartz substrate). However, in case of the EUVlithography process, it may be difficult to correct the maskregistration errors with a method of irradiating a laser onto a backside surface of the reflection type photo mask because the back sidesurface of the reflection type photo mask is covered with a conductivelayer.

SUMMARY

Various embodiments are directed to blank masks for extreme ultraviolet(EUV) lithography, methods of fabricating the same, and methods ofcorrecting registration errors thereof.

According to various embodiments, a blank mask for extreme ultraviolet(EUV) lithography includes a substrate having a first surface and asecond surface which are opposite to each other, a reflection layerdisposed on the first surface of the substrate to reflect extremeultraviolet (EUV) rays, an absorption layer disposed on the reflectionlayer opposite to the substrate to absorb extreme ultraviolet (EUV)rays, and a conductive layer disposed on the second surface of thesubstrate to expose portions of the substrate.

In various embodiments, the conductive layer may uniformly expose theportions of the second surface throughout the second surface.

In various embodiments, the conductive layer may include a chromenitride (CrN) layer.

In various embodiments, the substrate may have a plurality of trencheshaving a predetermined depth from the second surface, and the conductivelayer may be disposed in the trenches.

In various embodiments, the conductive layer may have a substantiallycheckerboard shape or a mesh shape in a plan view, and the blank maskmay further comprise an insulation layer on the exposed portions of thesecond surface.

In various embodiments, the insulation layer may include a materiallayer that transmits lights or rays.

In various embodiments, the blank mask may further comprise at least oneof a capping layer and a buffer layer between the reflection layer andthe absorption layer.

According to various embodiments, a method of fabricating a blank maskfor extreme ultraviolet (EUV) lithography includes forming a resistpattern on a back side surface of a transparent substrate to exposeportions of the back side surface, applying an etching process to theexposed portions of the back side surface to form trenches, removing theresist pattern after formation of the trenches, forming a conductivelayer in the trenches after removal of the resist pattern, andsequentially forming a laminated reflection layer, a capping layer andan absorption layer on a front side surface of the substrate opposite tothe conductive layer.

In various embodiments, the trenches may be formed to have a depth ofabout 70 nanometers to about 300 nanometers.

In various embodiments, the trenches may be uniformly arrayed throughoutan entire region of the back side surface to have a substantiallycheckerboard shape or a mesh shape in a plan view.

In various embodiments, forming the conductive layer in the trenches mayinclude depositing a conductive material on the back side surface of thesubstrate to fill the trenches and planarizing the conductive materialto expose the back side surface of the substrate.

In various embodiments, the conductive material may be planarized usingan etch back process or a chemical mechanical polishing (CMP) process.

In various embodiments, the conductive layer may be formed of a chromenitride (CrN) layer.

According to various embodiments, a method of fabricating a blank maskfor extreme ultraviolet (EUV) lithography includes forming an insulationlayer on a back side surface of a transparent substrate, patterning theinsulation layer to expose portions of the substrate, forming aconductive layer on the exposed portions of the substrate, andsequentially forming a laminated reflection layer and an absorptionlayer on a front side surface of the substrate opposite to theconductive layer.

In various embodiments, the insulation layer may be formed to have athickness of about 70 nanometers to about 300 nanometers.

In various embodiments, forming the conductive layer may includedepositing a conductive material that covers the patterned insulationlayer and the exposed portions of the substrate and planarizing theconductive material to expose the patterned insulation layer.

In various embodiments, the conductive material may be planarized usingan etch back process or a chemical mechanical polishing (CMP) process.

In various embodiments, the conductive layer may be formed of a chromenitride (CrN) layer.

According to various embodiments, a method of fabricating a blank maskfor extreme ultraviolet (EUV) lithography includes forming a conductivelayer on a back side surface of a transparent substrate, patterning theconductive layer to expose portions of the substrate, forming aninsulation layer on the exposed portions of the substrate, andsequentially forming a laminated reflection layer and an absorptionlayer on a front side surface of the substrate opposite to the patternedconductive layer.

In various embodiments, the conductive layer may be formed to have athickness of about 70 nanometers to about 300 nanometers.

In various embodiments, forming the insulation layer may includedepositing an insulation material that covers the patterned conductivelayer and the exposed portions of the substrate, and planarizing theconductive material to expose the patterned insulation layer.

In various embodiments, the insulation material may be planarized usingan etch back process or a chemical mechanical polishing (CMP) process.

In various embodiments, the insulation layer may be formed of atransparent insulation layer and the conductive layer is formed of achrome nitride (CrN) layer.

According to various embodiments, a method of correcting a registrationerror of a photo mask for extreme ultraviolet (EUV) lithography includesproviding a laser irradiation apparatus and a mask for extremeultraviolet (EUV) photolithography, irradiating laser beams onto themask using the laser irradiation apparatus, measuring permeability ofthe laser beams through an entire region of the mask to extract maskregistration errors, and compensating the mask registration errorsaccording to the measured permeability.

In various embodiments, the mask may be fabricated to include asubstrate having a first surface and a second surface which are oppositeto each other, a reflection layer disposed on the first surface of thesubstrate to reflect extreme ultraviolet (EUV) rays, an absorption layerdisposed on the reflection layer opposite to the substrate to absorbextreme ultraviolet (EUV) rays, and a conductive layer disposed on thesecond surface of the substrate to expose portions of the substrate.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other features and advantages of the disclosure willbecome more apparent in view of the attached drawings and accompanyingdetailed description, in which:

FIG. 1 is a perspective view illustrating a blank mask for extremeultraviolet (EUV) lithography according to an embodiment;

FIG. 2 is a cross sectional view illustrating a blank mask for extremeultraviolet (EUV) lithography according to an embodiment;

FIG. 3 is a plan view illustrating a back side surface of a blank maskfor extreme ultraviolet (EUV) lithography according to an embodiment;

FIG. 4 is a cross sectional view illustrating a blank mask for extremeultraviolet (EUV) lithography according to an embodiment;

FIGS. 5, 6 and 7 are cross sectional views illustrating a method offabricating a blank mask for extreme ultraviolet (EUV) lithographyaccording to an embodiment;

FIGS. 8 and 9 are cross sectional views illustrating a method offabricating a blank mask for extreme ultraviolet (EUV) lithographyaccording to an embodiment; and

FIG. 10 is a schematic view illustrating a method of correctingregistration errors of photo masks for extreme ultraviolet (EUV)lithography according to various embodiments.

DESCRIPTION OF SPECIFIC EMBODIMENTS

Various embodiments will now be described more fully with reference tothe accompanying drawings, in which various embodiments are shown.Various embodiments may, however, be embodied in many different formsand should not be construed as being limited to the embodiments setforth herein. Rather, these embodiments are provided so that thisdisclosure will be thorough and complete, and will fully convey theconcept of various embodiments to those of ordinary skill in the art. Inthe drawings, the thicknesses of layers and regions are exaggerated forclarity. Like reference designators in the drawings denote like orcorresponding elements, and thus their description will be omitted toavoid duplicate explanation.

FIG. 1 is a perspective view illustrating a blank mask for extremeultraviolet (EUV) lithography according to an embodiment, FIG. 2 is across sectional view illustrating a blank mask for extreme ultraviolet(EUV) lithography according to an embodiment, and FIG. 3 is a plan viewillustrating a back side surface of a blank mask for extreme ultraviolet(EUV) lithography according to an embodiment.

Referring to FIGS. 1, 2, and 3, a blank mask 100 for extreme ultraviolet(EUV) lithography according to an embodiment may include a masksubstrate 110 such as a transparent substrate, a laminated reflectionlayer 120 disposed on a front side surface of the mask substrate 110 toreflect EUV rays, a capping layer 130 (or a buffer layer 140), and anabsorption layer 150 sequentially stacked on a top surface of thelaminated reflection layer 120 opposite to the mask substrate 110, and aconductive layer 180 disposed on a back side surface of the masksubstrate 110 opposite to the laminated reflection layer 120.

The mask substrate 110 may include a material layer having a low thermalexpansion coefficient (LTE). For example, the mask substrate 110 may bea glass substrate or a quartz substrate.

The laminated reflection layer 120 may be formed by alternately stackinga plurality of first material layers 121 and a plurality of secondmaterial layers 122 having different optical characteristics from eachother. Thus, the laminated reflection layer 120 may correspond to aBragg reflector that exhibits a Bragg reflection phenomenon occurring atinterfaces between the first material layers 121 and the second materiallayers 122. For example, the first material layers 121 may be aplurality of high refractive material layers, and the second materiallayers 122 may be low refractive material layers.

In various embodiments, the laminated reflection layer 120 may include aplurality of molybdenum (Mo) layers having a relatively high refractiveindex and a plurality of silicon (Si) layers having a relatively lowrefractive index which are alternately stacked. That is, the laminatedreflection layer 120 may include the plurality of molybdenum (Mo) layersand the plurality of silicon (Si) layers disposed between the pluralityof molybdenum (Mo) layers. Alternatively, the laminated reflection layer120 may be formed by repeatedly stacking any one selected from the groupconsisting of a bi-layer of a molybdenum (Mo) layer and a beryllium (Be)layer, a bi-layer of a ruthenium (Ru) layer and a silicon (Si) layer, abi-layer of a silicon (Si) layer and a niobium (Nb) layer, a bi-layer ofa molybdenum carbide (MoC) layer and a silicon (Si) layer, a bi-layer ofa molybdenum compound layer and a silicon compound layer, and atriple-layer of a molybdenum (Mo) layer, a molybdenum carbide (MoC)layer and a silicon (Si) layer. The stack number of the bi-layer or thetriple-layer constituting the laminated reflection layer 120 may beequal to or greater than ‘30’ to obtain a reflectivity of about 50% orgreater. Alternatively, the stack number of the bi-layer or thetriple-layer constituting the laminated reflection layer 120 may beequal to or greater than ‘35’ to obtain a reflectivity of about 60% orhigher. In various embodiments, the stack number of the bi-layer or thetriple-layer constituting the laminated reflection layer 120 may bewithin the range of about 40 to about 60 to obtain a reflectivity ofabout 60% or greater. Further, the laminated reflection layer 120 mayhave a total thickness of about 210 nanometers to about 300 nanometers,but not limited thereto. For example, the total thickness of thelaminated reflection layer 120 may be determined in consideration of awavelength of the EUV rays used in the EUV lithography process.

The capping layer 130 stacked on the laminated reflection layer 120 mayprotect the laminated reflection layer 120. In various embodiments, thecapping layer 130 may include a silicon oxide (SiO₂) layer or a silicon(Si) layer. The capping layer 130 may suppress oxidation orcontamination of the laminated reflection layer 120 and may prevent thelaminated reflection layer 120 from being damaged when the absorptionlayer 150 on the capping layer 130 is patterned.

The buffer layer 140 and the absorption layer 150 may be sequentiallystacked on the capping layer 130. In various embodiments, the bufferlayer 140 may include a silicon oxide (SiO₂) layer, and the absorptionlayer 150 may include one of material layers which are capable ofabsorbing the EUV rays. For example, the absorption layer 150 mayinclude a conductive absorption layer such as a tantalum containinglayer, for example, a tantalum nitride (TaN) layer. The tantalumcontaining layer may be more readily etched by a plasma etching processutilizing fluorine type radicals which are widely used in fabrication ofsemiconductor devices. Thus, the absorption layer 150 may be formed ofthe tantalum containing layer. However, the tantalum containing layer ismerely an example of suitable materials for the absorption layer 150.That is, the absorption layer 150 may be formed of any material havingan appropriate absorptivity to the EUV rays.

The capping layer 130 and the buffer layer 140 may be optional elements.For example, at least one of the capping layer 130 and the buffer layer140 may be disposed between the laminated reflection layer 120 and theabsorption layer 150.

An anti-reflective layer 160 and a resist layer 170 may be additionallyand sequentially stacked on a top surface of the absorption layer 150opposite to the laminated reflection layer 120.

The conductive layer 180 may be disposed on the back side surface of themask substrate 110 opposite to the laminated reflection layer 120, asdescribed above. The conductive layer 180 may be, for example, a chromenitride (CrN) layer. When the blank mask 100 is loaded into an EUVlithography apparatus or other apparatuses, the conductive layer 180 mayact as an electrical adhesion layer for attaching the blank mask 100 toan electrostatic chuck of the EUV lithography apparatus or the otherapparatuses. Further, the conductive layer 180 may be partially disposedon the back side surface of the mask substrate 110 to expose portions ofthe mask substrate 110. This is for allowing lights or rays to penetratethe mask substrate 110 through the exposed portions of the masksubstrate 110 during a process for correcting a registration of theblank mask 100. Measurement and correction of the mask registrationerror may be performed throughout the blank mask 100. Thus, theconductive layer 180 may be disposed on the back side surface of themask substrate 110 such that the exposed portions of the mask substrate110 may be uniformly and regularly arrayed throughout the back sidesurface of the mask substrate 110.

In various embodiments, the conductive layer 180 may be disposed to filltrenches which are formed by etching the mask substrate 110 to a certaindepth, as illustrated in FIGS. 1 and 2. In addition, the conductivelayer 180 may be disposed to have substantially a checkerboard shapeincluding a plurality of segments when viewed from a plan view, but notlimited thereto. The size of each of the segments (i.e., d) constitutingthe substantially checkerboard shape and spaces therebetween may beadjusted such that lights or rays used in correction of the maskregistration error appropriately penetrate the mask substrate 110.

As described above, because the conductive layer 180 for attaching themask substrate 110 to an electrostatic chuck may be disposed tosubstantially have a checkerboard shape partially and uniformly exposingportions of the mask substrate 110, lights or rays may be irradiatedonto the back side surface of the mask substrate 110 to successfullyperform a process of correcting the mask registration error. As aresult, reliable EUV photo masks may be fabricated by successfullycarrying out the process of correcting the mask registration error.

FIG. 4 is a cross sectional view illustrating a blank mask for extremeultraviolet (EUV) lithography according to an embodiment. To avoidduplicate explanation, descriptions to the same elements as set forth inthe previous embodiments illustrated in FIG. 2 may be omitted or brieflymentioned in these embodiments.

Referring FIG. 4, an insulation layer 175 may be disposed on a back sidesurface of a mask substrate 110 to have holes exposing portions of theback side surface of a mask substrate 110. The holes of the insulationlayer 175 may be filled with a conductive layer 180. The conductivelayer 180 may include a chrome nitride (CrN) layer and may have asubstantially checkerboard shape in a plan view. However, the shape ofthe conductive layer 180 may not be limited to the checkerboard shape.For example, the conductive layer 180 may have any other shape (e.g., amesh shape or the like) that allows lights or rays used in correction ofmask registration errors to uniformly penetrate the mask substrate 110.

In an embodiment, the insulation layer 175 may be a material layer thattransmits lights or rays used in correction of mask registration errors.According to the previous embodiment illustrated in FIGS. 1 to 3, theconductive layer 180 may be formed by etching portions of the masksubstrate 110 to form trenches having a certain depth and by filling thetrenches with a conductive material. Additionally, according to anembodiment, the conductive layer 180 may be formed by depositing atransparent insulation layer 175 on the back side surface of the masksubstrate 110, by patterning the transparent insulation layer 175 toform holes therein, and by filling the holes with a conductive materialwithout etching the mask substrate 110. That is, the transparentinsulation layer 175 may act as a portion of the mask substrate 110.

According to an embodiment, the conductive layer 180 may be formed toallow the lights or rays used in correction of mask registration errorsto uniformly penetrate the mask substrate 110 without use of an etchingprocess for forming trenches in the mask substrate 110. Thus, etchdamage applied to the mask substrate 110 and/or contamination of themask substrate 110 can be minimized or suppressed. Further, the masksubstrate 110 may be attached and fixed to an electrostatic chuckbecause of the presence of the conductive layer 180 during a process forcorrecting the mask registration errors. This may lead to fabrication ofhigh reliable photo masks.

In various embodiments, formation of the conductive layer 180 may befollowed by formation of the transparent insulation layer 175. That is,the conductive layer 180 may be formed on the back side surface of themask substrate 110 and may be patterned to form holes exposing portionsof the back side surface of the mask substrate 110, and the holes of theconductive layer 180 may be filled with the transparent insulation layer175.

In various embodiments, the conductive layer 180 may include atransparent conductive layer, for example, an indium tin oxide (ITO)layer. In such a case, since the transparent conductive layer 180 mayallow penetration of lights or rays and use of an electrostatic chuck,the insulation layer 175 may include an opaque material layer that doesnot transmit lights or rays.

FIGS. 5, 6, and 7 are cross sectional views illustrating a method offabricating a blank mask for extreme ultraviolet (EUV) lithographyaccording to an embodiment.

Referring to FIG. 5, a mask substrate 110, for example, a transparentmask substrate may be provided. The mask substrate 110 may include afront side surface 110 a (i.e., first surface) and a back side surface110 b (i.e., second surface) facing each other. The mask substrate 110may be formed of a material having a low thermal expansion coefficient(LTE). For example, the mask substrate 110 may be a glass substrate or aquartz substrate.

A plurality of trenches 112 maybe formed in the mask substrate 110adjacent to the back side surface 110 b thereof. Specifically, a resistlayer may be coated on the back side surface 110 b of the mask substrate110. The resist layer may then be patterned using an exposure processwith electron beams or lasers and using a development process to exposeportions of the back side surface 110 b of the mask substrate 110.Subsequently, an etching process may be applied to the exposed portionsof the back side surface 110 b of the mask substrate 110, therebyforming the trenches 112 having a depth of about 70 nanometers to about300 nanometers. The etching process for forming the trenches 112 may beperformed using a dry etching technique that employs a mixture of acarbon tetra fluoride (CF₄) gas, an oxygen (O₂) gas and a helium (He)gas as an etching gas. Each of the trenches 112 may be formed to have awidth W of about 10 micrometers to about 50 micrometers, and thetrenches 112 may be arrayed substantially along an X-axis and a Y-axisto form a matrix shape when viewed from a plan view.

Referring to FIG. 6, the patterned resist layer may be removed and acleaning process may be applied to the mask substrate 110 where thepatterned resist layer is removed. A conductive layer 180 a may then beformed to fill the trenches 112 on the back side surface 110 b of themask substrate 110. The conductive layer 180 a may be formed of a chromenitride (CrN) layer using a general deposition process. The conductivelayer 180 a may be formed to a sufficient thickness to fill the trenches112.

Referring to FIG. 7, the conductive layer 180 a may be planarized usingan etch back process or a chemical mechanical polishing (CMP) process toform conductive layer 180 only in the trenches 112. Subsequently,although not shown in the drawings, a laminated reflection layer, acapping layer and/or a buffer layer, an absorption layer and ananti-reflective layer may be deposited on the front side surface 110 aof the mask substrate 110 using general processes, thereby forming abank mask for extreme ultraviolet (EUV) lithography illustrated in FIG.1.

FIGS. 8 and 9 are cross sectional views illustrating a method offabricating a blank mask for extreme ultraviolet (EUV) lithographyaccording to another embodiment.

Referring to FIG. 8, a mask substrate 110, for example, a transparentmask substrate may be provided. The mask substrate 110 may include afront side surface 110 a and a back side surface 110 b facing eachother. The mask substrate 110 may be formed of a material having a lowthermal expansion coefficient (LTE). For example, the mask substrate 110may be a glass substrate or a quartz substrate.

An insulation layer 175 may be formed on the back side surface 110 b ofthe mask substrate 110. The insulation layer 175 may be formed of atransparent material layer that transmits lights or rays used incorrection of mask registration errors. A thickness of the insulationlayer 175 may correspond to a thickness of a conductive layer which isformed in a subsequent process. That is, the insulation layer 175 may beformed to have a thickness which is substantially equal to the depth ofthe trenches 112 described in the previous embodiments. For example, theinsulation layer 175 may be formed to a thickness of about 70 nanometersto about 300 nanometers.

A mask layer 190 may then be formed on a side of the insulation layer175 opposite to the mask substrate 110. The mask layer 190 may be formedby coating a resist layer on the insulation layer 175, selectivelyexposing portions of the resist layer to electron beams or lasers, anddeveloping the exposed resist layer to expose portions of insulationlayer 175.

Referring to FIG. 9, the insulation layer 175 may be etched using themask layer 190 as an etch mask to expose portions of the mask substrate110. The mask layer 190, for example, the resist pattern may then beremoved. The etched insulation layer 175 may be formed such that theexposed portions of the mask substrate 110 have a substantiallycheckerboard shape, a mesh shape, or the like when viewed from a planview. Subsequently, a conductive material may be deposited on the etchedinsulation layer 175 and on the exposed mask substrate 110. Theconductive material may be a chrome nitride (CrN) layer. The conductivematerial may be planarized using an etch back process or a chemicalmechanical polishing (CMP) process to form a conductive layer 180remained only on the exposed mask substrate 110. As a result, theconductive layer 180 may be formed to have a checkerboard shape, a meshshape or the like when viewed from a plan view.

The following processes may be performed using the same manners asdescribed in the previous embodiments. Although an embodiment isdescribed in conjunction with an example that the conductive layer 180is deposited after formation of the insulation layer 175, the inventiveconcept is not limited thereto. For example, a conductive layer may bedeposited on the back side surface 110 b of the mask substrate 110 andpatterned to expose portions of the mask substrate 110, and aninsulation layer may be deposited on the patterned conductive layer andplanarized to expose a top surface of the patterned conductive layer.

Now, a method of correcting mask registration errors is describedhereinafter.

FIG. 10 is a schematic view illustrating a method of correctingregistration errors of photo masks for extreme ultraviolet (EUV)lithography according to various embodiments.

Referring to FIG. 10, a laser irradiation apparatus 200 and a samplemask 100 for extreme ultraviolet (EUV) lithography may be provided. Thelaser irradiation apparatus 200 may be an apparatus which is used in aprocess of correcting registration errors of a general photo mask. Invarious embodiments, the laser irradiation apparatus 200 may include alaser generator 210 for generating pulsed laser beams, an expander 220for enlarging an area on which the pulsed laser beams from the lasergenerator 210 are irradiated, a refractor 230 for guiding the enlargedlaser beams toward the sample mask 100, and a concentrator 240 forconcentrating the refracted laser beams.

The sample mask 100 for extreme ultraviolet (EUV) lithography mayinclude a mask substrate and a conductive layer 180 partially disposedon a back side surface of the mask substrate, as illustrated in FIGS. 1to 4. That is, the conductive layer 180 may have a substantiallycheckerboard shape, a mesh shape, or the like in a plan view. Theconductive layer 180 may be disposed to attach and fix the sample mask100 onto an electrostatic chuck and to expose portions of the back sidesurface of the mask substrate. Thus, sample mask 100 may partiallytransmit the laser beams through the exposed portions thereof.Accordingly, registration data of the sample EUV mask 100 may beobtained using the laser irradiation apparatus 200, and any registrationerrors may be corrected using the registration data of the sample EUVmask 100.

The laser beams concentrated by the concentrator 240 may be focused on acentral region of the sample EUV mask 100, and the focused laser beamsmay be scanned and irradiated onto the entire region of the sample EUVmask 100 with a constant beam density to obtain a uniform permeabilityof the sample EUV mask 100. Portions on which the focused laser beamsare irradiated may be deformed by the energy of the focused laser beams.

After the focused laser beams are irradiated onto the entire region ofthe sample EUV mask 100, the permeability may be measured throughout thesample EUV mask 100 to find out mask registration errors. If thepermeability of the sample EUV mask 100 is non-uniform, it may beunderstood that the sample EUV mask 100 has a registration error. Insuch a case, the laser beams may be controlled to have a higherintensity or a lower intensity, and the controlled laser beams may beirradiated onto the portions of the sample EUV mask 100 exhibiting arelatively low permeability or a relatively high permeability tocompensate the low or high permeability.

The embodiments of the inventive concept have been disclosed above forillustrative purposes. Those skilled in the art will appreciate thatvarious modifications, additions and substitutions are possible, withoutdeparting from the scope and spirit of the inventive concept asdisclosed in the accompanying claims.

What is claimed is:
 1. A blank mask for extreme ultraviolet (EUV)photolithography, the blank mask comprising: a substrate having a firstsurface and a second surface which are opposite to each other; areflection layer disposed on the first surface of the substrate toreflect extreme ultraviolet (EUV) rays; an absorption layer disposed onthe reflection layer opposite to the substrate to absorb extremeultraviolet (EUV) rays; and a conductive layer disposed on the secondsurface of the substrate to expose portions of the substrate.
 2. Theblank mask of claim 1, wherein the conductive layer uniformly exposesthe portions of the second surface throughout the second surface.
 3. Theblank mask of claim 1: wherein the substrate has a plurality of trencheshaving a predetermined depth from the second surface; and wherein theconductive layer is disposed in the trenches.
 4. The blank mask of claim1, wherein the conductive layer has a substantially checkerboard shapeor a mesh shape, and wherein the blank mask further comprises aninsulation layer on the exposed portions of the second surface.
 5. Theblank mask of claim 4, wherein the insulation layer includes a materiallayer that transmits lights or rays.
 6. The blank mask of claim 1,further comprising at least one of a capping layer and a buffer layerbetween the reflection layer and the absorption layer.
 7. A method offabricating a blank mask for extreme ultraviolet (EUV) photolithography,the method comprising: forming a resist pattern on a back side surfaceof a transparent substrate to expose portions of the back side surface;applying an etching process to the exposed portions of the back sidesurface to form trenches; removing the resist pattern after formation ofthe trenches; forming a conductive layer in the trenches after removalof the resist pattern; and sequentially forming a laminated reflectionlayer, a capping layer and an absorption layer on a front side surfaceof the substrate opposite to the conductive layer.
 8. The method ofclaim 7, wherein the trenches are uniformly arrayed throughout an entireregion of the back side surface to have a substantially checkerboardshape or a mesh shape in a plan view.
 9. The method of claim 7, whereinforming the conductive layer in the trenches includes: depositing aconductive material on the back side surface of the substrate to fillthe trenches; and planarizing the conductive material to expose the backside surface of the substrate.
 10. The method of claim 9, wherein theconductive material is planarized using an etch back process or achemical mechanical polishing (CMP) process.
 11. A method of fabricatinga blank mask for extreme ultraviolet (EUV) photolithography, the methodcomprising: forming an insulation layer on a back side surface of atransparent substrate; patterning the insulation layer to exposeportions of the substrate; forming a conductive layer on the exposedportions of the substrate; and sequentially forming a laminatedreflection layer and an absorption layer on a front side surface of thesubstrate opposite to the conductive layer.
 12. The method of claim 11,wherein the insulation layer is formed to have a thickness of about 70nanometers to about 300 nanometers.
 13. The method of claim 11, whereinforming the conductive layer includes: depositing a conductive materialthat covers the patterned insulation layer and the exposed portions ofthe substrate; and planarizing the conductive material to expose thepatterned insulation layer.
 14. The method of claim 13, wherein theconductive material is planarized using an etch back process or achemical mechanical polishing (CMP) process.
 15. A method of fabricatinga blank mask for extreme ultraviolet (EUV) photolithography, the methodcomprising: forming a conductive layer on a back side surface of atransparent substrate; patterning the conductive layer to exposeportions of the substrate; forming an insulation layer on the exposedportions of the substrate; and sequentially forming a laminatedreflection layer and an absorption layer on a front side surface of thesubstrate opposite to the patterned conductive layer.
 16. The method ofclaim 15, wherein the conductive layer is formed to have a thickness ofabout 70 nanometers to about 300 nanometers.
 17. The method of claim 15,wherein forming the insulation layer includes: depositing an insulationmaterial that covers the patterned conductive layer and the exposedportions of the substrate; and planarizing the conductive material toexpose the patterned insulation layer.
 18. The method of claim 17,wherein the insulation material is planarized using an etch back processor a chemical mechanical polishing (CMP) process.
 19. A method ofcorrecting a mask registration error, the method comprising: providing alaser irradiation apparatus and a mask for extreme ultraviolet (EUV)photolithography; irradiating laser beams onto the mask using the laserirradiation apparatus; measuring permeability of the laser beams throughan entire region of the mask to extract mask registration errors; andcompensating the mask registration errors according to the measuredpermeability.
 20. The method of claim 19, wherein the mask is fabricatedto include a substrate having a first surface and a second surface whichare opposite to each other, a reflection layer disposed on the firstsurface of the substrate to reflect extreme ultraviolet (EUV) rays, anabsorption layer disposed on the reflection layer opposite to thesubstrate to absorb extreme ultraviolet (EUV) rays, and a conductivelayer disposed on the second surface of the substrate to expose portionsof the substrate.